They say this is because so many different types of bacteria come together at sewage plants that it gives them the perfect opportunity to swap genes, allowing antibiotic-resistant bacteria to evolve much faster than they would in isolation.

Study leader Professor Wellington, along with colleagues from Warwick and Birmingham universities and the Health Protection Agency, analysed sediment samples from upstream and downstream.

They found bacteria resistant to important antibiotics used to treat a range of problems, including meningitis, septicaemia, and so-called hospital-acquired infections.

They also found resistant E. coli were seven times more common downstream of a UK sewage plant than upstream.

Their findings suggest resistance is spreading because of a gene called blaCTX-M-15 which bacteria collect to adapt to their environment.

Superbug

Professor Wellington said: “This is a big deal because this is the most common bacterial antibiotic resistance gene causing failures in treatment of infections, and it’s the first time anyone has seen this gene in UK rivers.”

The researchers say stricter regulations and higher levels of treatment are needed to halt the rise in antibiotic resistance in the environment.

A spokesman for Public Health England said the antibiotic-resistent bacteria posed no health risk to the public because the microbes were found in silt and there was no evidence they had entered tap water.

A spokesman for Severn Trent Water, which runs the sewage plant at Finham, said: “Severn Trent Water takes its environmental responsibilities extremely seriously.

“Earlier this month we received confirmation from our environmental regulator, The Environment Agency, that we have achieved a four star rating and leading company status for our environmental performance (we were the only company in the UK Water Industry to reach this standard).

“The development of antibiotic resistant strains of bacteria is without question an internationally important issue, and we are already engaged in increasing our knowledge to determine whether wastewater treatment has role to play in this area.

In conjunction with all the other UK water and sewerage companies, we are actively involved in a multi-million pound national research project to look at the levels of pharmaceuticals in the sewage entering our treatment works.

“The programme also looks at the removal efficiency of our existing treatment processes, and what additional treatment could be provided by ‘advanced’ treatment processes, to meet future standards if and when they are applied to the UK water industry.

“We will continue to work with Government, regulators and academia to further our understanding of this important issue.”

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